1. Field of the Invention
The present invention relates to an apparatus and method for the manufacture of subassemblies, particularly as used in the construction of automobiles and the like. Specifically, the invention is an apparatus and method which establishes a predetermined geometric relationship between at least two parts in a geometry station in the form of an end effector attached to the wrist head of a robot. The robot may be programmed to convey the geometry station to any one of a number of work performing devices located within a defined work region surrounding the robot to perform work on the at least two parts securely maintained in the geometry station.
2. Description of the Prior Art
In the construction of products such as automobiles, many subassemblies are first manufactured in off-line operations to be later assembled to form the final end product which travels along a production line. The subassemblies, themselves, generally include a multiplicity of elements or parts formed together in a given dimensional relationship, one to the other, and interconnected by various techniques such as welding, adhesives, mechanical fasteners and the like. For the purpose of obtaining a high quality end product, it is important that each subassembly conform to given parameters or specifications and that the dimensional stability of the subassembly be repeated from one subassembly to the other thereby assuring that each of the subassemblies when joined together form a quality final product fit together properly.
The modern production line has long recognized the advantages of assembling a complex product, such as an automobile, by the marriage of dimensionally conforming subassemblies. Many of the subassemblies are manufactured by the use of fixtures or jigs. Such fixtures or jigs are generally stationary or may move along a production line where computer controlled robots perform work operations upon the particular workpiece held within the fixture or jig. In this type of environment the robotic end effector must necessarily incorporate one or more tools to perform the desired work operations plus provide or otherwise accommodate the necessary power, energy requirements, and working material supply, to operate the end effector tools. Thus the end effector generally becomes very heavy and relatively complex thereby complicating the function, operation, and construction of the particular robot. Also, since some of the robots must travel some distance to have access to the parts clamped in the fixture or jig securely fixed on the production line, it is necessary to make appropriate provisions for the routing of hydraulic hoses, power supply lines, air supply lines, and the like. All of which lead to complication of the activities associated with production line operations due to the crowded workspace in which these functions are to be performed. To alleviate some of these problems some of the robot functions are combined through the use of exchangeable multi-function end effector tools as taught by U.S. Pat. No. 4,627,785. Further, efforts have been made towards increasing the efficiency of the operation of the robot by utilizing input taken from the robot's position to calculate a feedback as to the path the robot should be programmed for as is taught by U.S. Pat. No. 4,853,603.
Although it is not unknown to use computer programmable robots to position a given workpiece relative to a stationary tool, for application of work operations upon the workpiece as described in U.S. Pat. No. 4,853,603 entitled "Control of an Industrial Robot", or U.S. Pat. No. 4,605,569 entitled "Method and Apparatus for Panel Wiping Operation" it is unknown to provide a computer controlled robot with an end effector fixture, jig, or geometry station wherein the end effector serves to set the geometry of the subassembly elements, lock or hold them firmly in place relative to one another and present the geometrically oriented elements as a geometry station to one or more stationary work performing stations or tools to have desired work performed upon the geometrically oriented elements.